In your first picture can check what the 3 joined spots are in between the ribs - right in the center. It almost looks like they are some scale insects, but the picture is not of high quality enough.
As to the brown area of the plant near the roots: soft or squishy? And when did you water last, and where do you keep the plant light/temperature wise?
Soft does not have to be bad, squishy is almost always bad. Outwardly what you have photographed does not look too alarming. There could definitely be something going on with the plant health wise, but what you can see in the picture does not immediately scream rot, however there are plenty of bugs that may not make the plant rot, but still be affecting its healthy negatively.
